1. Field of the Invention
This invention relates to a working vehicle having a propelling clutch, a main change speed device and an auxiliary change speed device. More particularly, the invention relates to a shift control apparatus of this type of working vehicle.
2. Description of the Related Art
In a conventional working vehicle, when the auxiliary change speed device is shifted, the propelling clutch is operated automatically in an interlocked relationship thereto. Thus, an auxiliary change speed operation may be effected without requiring an additional operation to break power transmission from the engine to the auxiliary change speed device. However, in the conventional working vehicle, when the shift gear of the auxiliary change speed device is switched from a non-transmitting position to a transmitting position, the traveling device such as wheels is connected to the main change speed device through the auxiliary change speed device. After a shifting operation of the auxiliary change speed device is completed and before the propelling clutch is engaged, the main change speed device is in a state of transmitting power at a certain speed and has a relatively strong inertia to remain in that state. As a result, when the traveling device is connected to the main change speed device after the auxiliary change speed operation, the main change speed device imparts a resistance to the traveling device in inertial motion, which tends to produce a shock of change speed.